This invention relates generally to data communications networks, and more particularly, to a method and apparatus for encoding a station identifier and switch identifier which optimizes the amount of resources required for a network switch.
Computer networks are used to interconnect many computing resources, including computers, workstations, servers, printers, modems, and storage devices. For example, two or more computers may be connected together through a network. Network users are able to share files, printers and other resources, send messages and run applications on remote computers. An important part of any computer network includes the physical components or network communications devices used to interconnect the computing resources.
One network communications device used to interconnect multiple computing resources is a chassis-based system designed to accommodate a number of internal cards. The computing resources such as computers are coupled to the internal cards of the chassis-based system. Once the computers are coupled to the internal cards, the computers are coupled to the network. To accommodate network growth, additional internal cards may be purchased and added to the chassis-based system. With the additional internal cards installed, additional computing resources may be added to the network. A disadvantage of these chassis-based systems is that there is a relatively large initial investment when purchasing the chassis because of the large amount of overhead associated with chassis-based systems.
An alternative to expensive chassis-based systems is the use of less expensive standalone network communications devices or units that have a fixed number of ports for connecting computing resources or stations to the network. Such standalone network communications devices include stackable switches or the like. Although additional ports can not be added to each individual standalone unit, separate standalone units can be stacked, cascaded or coupled to accommodate network growth. As a result, there is a lower startup cost when establishing a computer network with the standalone units in comparison with chassis-based systems. Furthermore, network administrators still have the flexibility to increase the size of the network with the less-expensive standalone units.
FIG. 1 illustrates multiple network communications devices 103, 105, 107, 109 and 111 coupled together to form a computer network 101. Multiple computing resources (not shown) are coupled to each network communications device 103, 105, 107, 109 and 111. In one embodiment, network communications devices 103, 105, 107, 109 and 111 are stackable switches coupled together through bus 113. Bus 113 is used to tie together the switch network fabric of computer network 101. It will be noted by one of ordinary skill in the art that the utilization of bus 113 is an extension of the chassis-based designs discussed earlier. The internal cards of the chassis-based systems are commonly coupled to high speed buses within the chassis-based systems.
While the use of stackable switches allows a network to be easily upgraded to accommodate additional ports, an important consideration is to keep the cost of each switch low. As additional switches and ports are added to the network, each switch on the network must contain a list of all other switches and ports. However, the memory required to store information on all ports on the network may become large, even for average sized networks. For example, in a network using stackable switches having 64 ports each, with a maximum total of eight switches, each switch would be required to store information for all 512 ports. Therefore, there is a need for a way to store port information which optimizes the amount of resources required for a network switch.
The present invention provides a method and apparatus for providing data communication between stations on a network which optimizes the amount of resources required for a network switch. A first data frame is encoded with a source station identifier for the first station and a source switch identifier for the first switch. The first data frame is sent from the first switch to the second switch. A station list in the second switch is updated to indicate that the first station is associated with the first switch. Subsequent data frames having the same destination as the first switch are sent directly to the second switch. Any switch on the network need only identify the local ports attached to the switch, plus the number of switches on the network. The task of identifying all of the ports on the network is distributed across all switches on the network.